Train control



Jan. 2, 1934. O H IKE ET AL 1,942,138

TRA'IN CONTROL Fi1ed April 26, 1922 4 Sheets-Sheet 2 ad I VENTORM ATTdRNEY Jan. 2, 1934.

DECKE ET AL 4 Sheets-Sheet 3 wmm mm mm no SN 8N s E HW 1m 8- N SM m \QON I h m aOON OON\ OON o K V mu Pi Jan. 2, 1934. o) H. DlCKE ET AL.

TRAIN CONTROL Filed April 26, 1922 4 Sheets-Sheet 4 ATTORN EY 3h l o2. o mrm FM I Km omrm orm Patented Jan. 2, 1934 UNITED STATES TRAIN CONTROL Oscar H. Dicke and Neil D. Preston, Rochester, N. Y., assignors to General Railway Signal Company, Gates, N. Y., a corporation of New York Application April 26, 1922. Serial No. 556,714

Claims. (Cl. 246-63) This invention relates to the method and means for transmitting control influences for automatic train control systems.

In automatic train control systems, it is necessary to transmit control influences from the trackway to a passing vehicle in response to the change of tramc conditions in advance. In systems of this kind, it is desirable to provide such a transmitting means which is continuous in its character, that is,'one in which the control influence is always present except when a danger trafllc condition exists. Some of the advantages of continuous control are that when danger traflic conditions in advance clear up, the train is permitted to accelerate at the moment such change of traffic condition takes place; and further, if the trackway in advance of the vehicle should change from a certain condition to a more dangerous condition, such change will be transmitted to the vehicle immediately, thereby governing it accordingly. A further and. important feature of a train control system of the continuous type is that it carries out the maxim of having the failure on the side of safety, that is, the communicating means is what permits the train to proceed, and consequently any failure thereof will control the train on the side of safety by causing it to stop or be otherwise subjected to the control corresponding to danger ahead.

A continuous control system is preferably of the type in which an influence is communicated in an occupied block and on account of this requirement, it is desirable to have current flowing in a circuit including the track rails in such a way that this current may be shunted by another train in said block and cut ofi from the following train. Along this line it has been proposed to supply alternating signaling current along the track rails and provide means for detecting its presence and its character. One objection to a system of this kind is the necessity of supplying a source of alternating current at all points along the track where such continuous control is to be effected. For this reason a failure of the necessary transmission lines, due to storms, sleet, lightning, and the like, often disables a considerable stretch of the system. Also, systems of this kind arerather expensive to install where direct current block signaling systems have already been installed, because an additional supply of alternating current solely for train control purposes must be added.

Among the principal objects and purposes of the present invention, are to devise a method and means of providing continuous control and release inductively from the trackway to moving trains, which will have all of the advantages of a continuous inductive control system but will not require a supply of alternating'current along the track, so that the system of train control may be readily applied to direct current block signal systems without expensive additions or modifications, and so that failures of the trackway equipment will be localized and will affect the movement of trains in the particular defective track circuit or block only.

Generally stated, the underlying principle of the method and means of this invention consists in utilizing a suitable supply of energy carried wholly on the train itself to produce by induction in regular track rails a signaling current which is controlled or modified automatically in accordance with the presence or absence of another train ahead, either directly through the shunting action of the wheels and axles of that train ahead, or through the agency of well-known track circuits; and this current, when thus controlled or modified to conform with clear or caution traffic conditions ahead, as the case may be, is again inductively taken up on the same train, amplified as required, and finally used to influence electroresponsive means and manifest by such influence the nature of the traffic conditions ahead, whether proceed, caution, or stop. Various specific characteristic features of the invention involved in carrying out this general principle of operation will be explained as the description progresses.

In describing the invention in detail, reference will be made to the accompanying drawings which show the invention in a simplified manner, more for the purpose of making it easy to understand its principle and mode of operation than with a view of illustrating the particular parts and circuits preferably employed in practice, and in which:

Figure 1 diagrammatically illustrates one embodiment 'of the present invention, in which two- ,condition control of clear or danger is obtained;

Fig. 2 is a diagrammatic sectional view taken through the trackway directly ahead of the receiving elements of Fig. 1;

Fig. 3 illustrates another form of the invention. in which three-condition continuous control, corresponding to clear, caution, and stop, may be 105 obtained in a territory having either direct or alternating current track circuits and with either end of the vehicle running ahead;

Fig. 4 illustrates another form of the invention. in which current is induced into a circuit which 110 is independent of the running rails of the tracky;

Figs. 5, 6 and '7 show diagrammatically modifled forms of inducing and receiving elements;

Fig. 8 illustrates still another form of the invention, in which current is induced into and received from the same circuit in the track rails; and

Fig. 9 illustrates a trackway system employing partially alternating current track circuits and partially direct current track circuits, in which the trackway equipment is constructed and arranged to facilitate continuous train control in cooperation with the same car-carried apparatus.

In the embodiments of the invention illustrated, the transmission of the continuous control influences are produced by alternating current flowing in the track rails ahead of the train in each block of the usual block signaling system, while the train is in that block. This alternating signaling current of each block is preferably modified or suitably controlled by a track circuit of the block next in advance so as to produce on the train an appropriate influence corresponding to the presence or absence of another train ahead. Various arrangements of track and control circuits suitable for controlling the flow of this alternating current may be employed, and it should be understood that the arrangement of trackway circuits illustrated is merely a typical illustration.

In each of the embodiments of the invention illustrated, the track rails 1 and 2 are divided into blocks by insulated joints 3 in the usual way, one block I and the adjacent ends of two other blocks H and J being shown. These parts and circuits associated with the various blocks, which are the same or function the same, have for convenience been given like reference characters, with distinctive exponents. Each of the blocks is provided with a source of current, as a track battery 4, and also a track relay 5, the same as in ordinary block signal systems. The invention may be used with, or without, the usual fined signals, de-

pendent upon the type of train control apparatus; and we have illustrated such fixed signals S conventionally, without attempting to illustrate their well-known control circuits and devices. In the various embodiments of the invention illustrated, the normal direction of trafiic has been indicated by a large arrow D'I', substantially midway between the track rails. Structure of Fig. 1.-In Fig. 1 has been illustrated a, simplified arrangement for obtaining continuous information and control on a train dependent on trafiic conditions in advance thereof. In the simplified arrangement shown in this Fig. 1, only two-condition control is provided, that is, an indication of whether the block, in which the train equipped with this apparatus is moving, is occupied by another train, or if the 'next block in advance thereof is occupied, or if both of these blocks are clear as far as the train in question is concerned. This continuous control is effected by inducing current in a loop circuit including the two rails of the trackw-ay ahead of the train, which current, by the aid of a suitable transformer, will induce a current in a receiving circuit, which comprises one of the rails and a return line wire, thereby permitting this latter current 'to be detected if traflic conditions ahead are clear.

Directly in front of the first axle of the vehicle are provided inducing elements IE. Each of these elements, as shown, comprises a U-shaped lami- .forces of the winding and minimizes the disadvantages of leakage. Obviously, the winding may extend throughout the length of the core, if desired, or may be local on the legs or back yoke, accordingly as best suited for the particular working conditions encountered. The coils 8 of the inducing elements IE are preferably wound and are connected in series in a manner so that, if alternating current is supplied thereto, the flux emanating from the pole pieces '7 will encircle the track rails 1 and 2 in different directions, that is, so that one element at a given instant will induce a voltage in its corresponding rail directed away from the train, whereas the other element will induce a voltage in its rail directed toward the vehicle. This circuit for coi-ls 8 is energized from a suitable alternating current generator 9, and may be traced as follows:Beginning at the terminal or brush 10 of the alternating current generator 9, wire 11, coils 8 of one of theinducing elements IE, wire 12, coils 8 of the other inducing element IE, wire 13 back t'othe other terminal or brush 14. of the generator 9. Y

This alternating current generator 9 is preferably designed and operated to produce a frequency, distinctive from commercial frequencies, and reasonably high, which may for example be about 500 cycles per second, although, this frequency may, it is believed, be hgher or lower, ranging for instance from 60 cycles to 3000 cycles per second. The reason for preferably employing a higher frequency than the usual lighting and power frequency, is that it facilitates the induc tion of voltage into a cfrcuit, and also permits the detection of such current by induction through an intervening air gap much more effectively than does a lower frequency. The frequency employed should, however, be selected with due regard to the fact-that the inductive reactance of the rails increases with the frequency and therefore hinders the transmission of high frequency current therethrough. The alternating current generator 9 may be driven by a turbine receiving steam from the locomotive, or it may comprise the generator of a motor generator-set running off of a battery floated across a source of direct current supply. If desired, two such sets may be provided to insure a continuous supply of alternating current.

f The circuit in which current flows due to the action of these inducing elements IE, which for convenience will be termed a loop circuit hereinafter, may be traced as follows :--Beginning at the track rail 1, battery 4, primary winding 15 of the transformer P, track ml 2, wheels and axle 16 of the vehicle equipped with this train contion of flow of this current being represented by the dotted arrows. This transformer may be of any construction suitable for the transformation of current of the signaling frequency used. The ratio of transformation in the transformer P should be selected or varied in practical operation to fit the specific working conditions encountered.

It should be noted that, if a train employing a plurality of cars is passing along the track, part of this current may flow through the rear axles of the train across between the rails, so that there may be some current in both of the track rails 1 and 2 at the rear end of the locomotive; and in order to detect all of this current two receiving elements RE have been provided.

Each of these receiving elements RE comprises a U-shaped core 24, preferably constructed of a high grade of laminated iron, which terminates in enlarged pole pieces 25, and is provided with a winding or coils 26. The coils 26 of these receiving elements RE are preferably connected in series so that the voltages induced therein due to the magnetism caused by the current fiowing in the receiving circuit, that is, the current fiowing in the two rails in multiple, will be cumulative. In order to improve the functioning of this receiving element, and also to segregate and avoid amplification of currents of frequency somewhat dif-' ferent from the specific signaling frequency of the train in question, a condenser 27 is preferably connected in multiple with the coils of said element; and this complete receiving circuit, comprising wires 28, 29, 30 and condenser 27, is connected to an input circuit, which includes wires 31 and 32, of a suitable amplifying organization or device, designated as a whole A.

This amplifying device A may be of any desired type and may employ any number of stages of amplification, but has for simplicity been shown as a two-stage amplifier set, employing-two thermionic or vacuum tube amplifiers of the threeelement type, which for convenience will be termed audions. The audion 33 is provided with a filament 34, a grid 35, and a plate 36; and the audion 37 is similarly provided with a filament 38, a grid 39, and a plate 40. The filaments 34 and 38 are heated by a filament battery 41. The wire 31 is connected to the filament 34, and the other wire 32 is connected to the grid 35, through blocking condenser 44 and wire 45. This blocking condenser 44, serves its usual purpose, familiar to those skilled in the art. A grid-leak, comprising a high ohmic resistance, across this condenser or inserted between the grid 35 and the filament 34, together with other expedients well-known by those skilled in the art pertaining to amplifiers of this kind, may be employed.

The plate circuit of the audion 33 may be traced as followsz-Beginning at the filament 34, wire 46, plate battery 47, wire 48, primary winding 49 of the transformer T, wire 50, plate 36, through the audion back to the filament 34.

The grid circuit of the audion 37 may be traced as followsz-Beginning at the filament 38, wire 51, secondary winding 52 of the transformer T, wire 53, to the grid 39 of the audion 37.

The plate circuit of the audion 37, or output circuit of the amplifying combination, -may be traced as follows:-Beginning at the filament 38 of the audion 37, wires 54 and 46, plate battery 47, wires 55 and 56, to a suitable electro-responsive device, which in this instance comprises one winding 57 of a relay R, wires 58 and 59, plate 40 back to the filament 33. A condenser 43 is preferably connected across the field winding 57 of the relay R to balance its inductive reactance; and this condenser is selected or adjusted in practice to tune the circuit for said field coil to resonance for the particular signaling frequency of the train question.

The other or local field 60 of the relay R is energized by the alternating current generator 9, through a circuit which may be traced as follows:-.Beginning at the terminal .10 of the generator 9, wire 61, local field winding 60 of the relay R, wire 62 back to the terminal 14 of the generator 9. a

The relay R may take various forms; and as shown conventionally, it is a two-element alternating current relay, either of the vane or induction type, commonly used in the railway signaling art. It should be understood, however, that it is contemplated in connection with this invention that relays of the dynamometer type, or in fact any form of electro-responsive device suitable for the purpose andhaving the desired efficiency of performance, may be used. In the type of relay shown, the torque or operating force ceases when current is cut off from one field, even though the other field may still be energized. 1 Also, this relay requires a certain degree of phase displacement of the currents in its two-field windings to produce a torque. These, and other operating and structural characteristics of the twoelement alternating current relay employed, are well recognized in the art; When used in connection with this particulefr invention, such twoelement relay is preferably designed in accordance with well-known principles to derive most of its operating energy from its so-called local 11 field winding, that is, the winding which is directly energized from the generator. This is done so that the amount of energy needed in the other field winding for operating the relay, which is derived from the trackway, may be relatively small. This relay R is provided with a suitable circuit controlling arrangement and in accordance with well-known practice has a bias to the neutral or deenergized position. In the simplified arrangement shown, the movable element or contact finger of the relay is biased by a spring. In practicing the invention it should also be borne in mind that the relay, together with the other sensitive parts of the car equipment, should be suitably housedand protected against jar and 125 vibration; but since these specific expedients form no part of the present invention, illustration and description thereof has been omitted.

When the relay R is energized, a circuit is maintained closed through the train control device K, which may be traced as follows:--Beginning at the battery 65, wire 66, movable contact 67 of the relay R, wire 68, winding of the train control device K, wire 69 back to the battery 65,.thus maintaining a suitable train control device K energized so long as the relay R is energized. This train control device, when it has been deenergized by the dropping of the relay R, may be used to apply the brakes at once, or give a brake application dependent upon the speed of the train at the time, the acceleration or deceleration of the train, or whether the brakes are applied at the time, and the like. In short, the device K, when deenergized, may impose any form of control desired, or merely give a warning signal. Since, however, the particular construction of this train control device is no part of the present invention, such a device has been merely conventionally illustrated.

Operation of Fig. 1.-Let us assume that a 150 vehicle is moving in the block I under clear traffic conditions ahead in the block I as well as in theblock J, as illustrated. Under these conditions,

the inducing elements IE will induce a current in the loop circuit as illustrated by the solid arrows which in turn, through the windings l5 and 1'? of the transformer P, will cause the flow of a current, as indicated by the dotted arrows in the receiving circuit. This current in the receiving circuit will induce a current in the coils 26 of the receivingelements RE which, by the aid of the condenser 27 and the blocking condenser 44, will impress a voltage on the grid 35 of the audion 33 corresponding to the current flowing in the receiving circuit just mentioned. "The impression of'this voltage on the grid 35 causes the internal resistance of the plate circuit of the audion 33 to change substantially proportionally, thereby causing the fiow of a pulsating current in this plate circuit. This current will be transformed through the transformer '1, thereby impressing a voltage on the grid 39 of the audion 3'7 which has a definite phase relation with respect to the voltage impressed on the grid 35, but is highly magnified or amplified. The impression of this highly amplified voltage on the grid 39 causes a pulsating current to flow in the plate circuit of this audion 37, which includes the secondary field winding 57 of the relay R. This pulsating current will act on the current flowing in the local field 60 of this relay R to produce a torque to maintain movable contact 67 closed against the tension of the spring 70 of this relay, thereby maintaining the train control device K energized and ineffective to f restrict the speed of the train.

As previously stated, the two-element type of induction relay R assumed to be used requires a phase displacement of the currents in its field windings to produce an operating torque. This desired phase displacement is obtained by properly designing or proportioning the circuits over which current is supplied to the field windings from the generator 9. One field winding so is directly connected to the generator; and assuming the current in this field winding 60 to be in phase with the voltage of the generator, the desired phase displacement for operation of the relay R may be obtained by causing the current.

in the other field winding 57 to lag through the desired angle, preferably electrical degrees, by making reactive any of the circuits or electrical connections intervening between the generator and the field winding 57.

Let us assume, now, that the block J is occupied .when the train in question enters the block I.

The train in the block J robs the track relay 5 of its current, thereby causing it to drop its front contact 19 ,.thus opening the receiving circuit heretofore traced. Obviously, since this receiving circuit has been entirely interrupted, the receiving elements RE will not be influenced and the relay R will be deenergized, thus deenergizing the train control device K, which will restrict the movement of the train in a manner dependent upon the construction of this device K.

Let us assume, now, that the block I is occupied by another train ahead at the time the train in question equipped with the apparatus illustrated is entering the block I. Under this condition, the train ahead occupying the loop circuit in front of the train in question shunts the pri-' gized, thus actuating the train control device K in the same manner as heretofore set forth.

Let us assume, now, that the train ahead occupying the loop circuit ahead of the train in' question leaves the block I and enters the block J. Although the transformer P is no longer shunted, no clearing influence will be received at the com trol relay R, because the receiving circuit is open at the front contact 19 of track relay 5 Let us assume, now, that this train ahead en tirely leaves the block J. This will cause the track relay 5 to become energized, thereby closing its front contacts 19 and transmitting a clearing influence at the instant tramc conditions ahead clear up which influence will again energize the relay R, and permit the train to proceed um'estricted immediately.

The condenser 21 has been provided in the receiving circuit for the purpose of insulating the opposite ends of the track rail 1 of a particular block, except through this rail itself, so that if a rail should break, direct current can not flow through the wire 22 to energize the track relay pedance may be substituted for the condenser 21,

if desired, this resistance or impedance being of a value to limit the flow of direct current to an amount insuficient toenergize the track relay 5. Although a two-element relay R has been shown, it should be understood that a single element relay energized entirely by the receiving elements RE through suitable amplifiers may be employed. A single element relay may, under certain conditions, be preferable, because the functioning of a relay of this type is entirely independent of phase relation, which is a variable factor, dependingupon the position of train in the block and upon the condition of the track circuit. Where a two-element relay of the induction type is used, as shown, the currents in the two fields of this relay should have a maximum phase displacement for eiiicient operation. Special provisions for obtaining such phase displacement may be made wholly on the train, wholly on the track, or partly on both. Also,'if desired, the generator may have a separate phase winding thereon, for the purpose of energizing the local held of the relay. Generally speaking, it is considered preferable to have some at least of the phase displacement, in addition to that caused by the inherent reactance of the track rails, obtained by devices wholly on the track, since this facilitates adjustment and compensation for different length blocks, different conditions of ballast, and the like.

Structure of Fig. 3.In Fig. 3 of the drawings has been illustrated a modified form of the invention shown in Fig. 1. Since certain of the elements are the same as those illustrated in Fig. 1, they will be given like reference characters. The trackway apparatus of the block I is in many respects similar to that of the apparatus illustrated in Fig. 1, the principal distinction being that the line circuit is connected to the middle point of a balancing resistance BR at each end of the block instead of being connected to the track rail 1; and that provision has been made for changing the relative instantaneous rail polarity of the receiving circuit with respect to the loop circuit by pole-changing contacts actuated by the relay 5 In order to facilitate the movement of the locomotive or other vehicle carrying the inducing elements IE at the front end and the receiving elements at the rear end, past the insulated joints at the entrance to a block without interruption of the continuous influence, provision is preferably made to extend, so to speak, the receiving circuit of each block back for a short distance at the exit end of the block next in the rear, so that at the time the inducing element of the vehicle passes the joints, the receiving element of that vehicle may influenced by the current in the receiving circuit of the block the vehicle is just entering. This may be done, as shown, by making the connections between the track rails and the balancing resistance BR at the entrance end to each block by conductors extending back of the insulated joints of that block close to and parallel with the track rails so as to affect the receiving elements. These conductors may be lengths of insulated wires fastened directly to the track rails, or may be sections of additional track rails, or the like. The length of these auxiliary conductors should correspond approximately with the distance between the inducing element and receiving element on a locomotive.

It is noted here that this same expedient may be added to the arrangement shown in Fig. 1, and also that such overlapping of conductors may be altogether omitted, if desired, and satisfactory operation obtained provided the train control device K, or some element of its control means, is made sufficiently slow acting to avoid .the imposition of an unfavorable control during the time the insulated joints bar the flow of current from the inducing elements to the receiving elements.

This receiving circuit may be traced as follows:-Beginning at the secondary winding 17 of the transformer P, wire '75, front contact 76 wire 7'7 wire '78 to the middle point of balancing resistance BR, through the track rails 1 and 2 in multiple to the balancing resistance BR at the exit end of the block, through wire '79, front contact 80*, wire 81 back to the secondary winding 17 of the transformer P.

It is considered that the system of this inven tion, employing a source of alternating current on the car, is specially adapted for territory equipped with direct current track circuits, since it permits the application of a train control system of the continuous inductive type to such direct current territory without need of adding expensive trackway sources of energy. However, on those railroads or divisions where alternating current track circuits are used, or where a suitable reliable source of alternating current along the track is already available, it might be considered preferable to use the alternating current already at hand for train control purposes; but since it may be necessary for the same locomotive or other vehicle to travel in both the direct current and alternating current territories, it is proposed here to provide a form of car apparatus which will be readily converted so as to work in either territory. To facilitate explanation of this feature of the invention, the block J has been shown in Fig. 3 as having an alternating current track circuit supplied from a transmission line 82 along the track, it being expected that energy from this transmission line will be used for train control purposes.

In the block J has been illustrated a transmission line, comprising wires 82 which are connected to the primary winding 83 of a suitable transformer. This transformer is provided with two secondary windings, one of which, namely, winding 84 isused for energizing the loop or track circuit, whereas the other winding 85 is used for energizing the receiving circuit heretofore mentioned. The instantaneous current flow-- ing in the track circuit will be illustrated by solid. arrows, whereas the'current flowing in the receiving circuit will be indicated by dotted arrows. The track circuit may be traced as followsz-r-Beginning at the secondary winding 84 wire 74 ,v track rail 2, track relay 5 rail 1, wire 86 adjustable impedance 8'7 back to the secondary winding 84 The receiving circuit may be traced as follows:Beginning at the secondary transformer winding 85 wire 88 movable contact 89*, wire 90 to the middle point of the balancing resistance BB through track rails 1 and 2 in multiple, to the middle point of the other balancing resistance BB at the exit end of the block, wire 91 front contact 92*, wires 93 and 94 back to the secondary transformer winding 85 It is thus noted that under clear traffic conditions of the block J, two independent alternating currents will be flowing in the track rails of the block, one of these currents flowing in opposite directions in the rails, whereas the other current flows in the same direction through the rails in multiple. These currents preferably have their phases displaced substantially 90 degrees, such displacement being accomplished by inserting resistances in one of the inductive reactive circuits, preferably the receiving circuit, or if desired these circuits may be energized from different phases of a polyphase transmission line.

The car-carried apparatus illustrated in Fig. 3 is of a character so that if direct current block signal territory is encountered, a suitable doublethrow switch'DS may be closed in one direction, whereby train control influence communicating means is provided which operates on the principle wherein the energy is supplied from the train, similar to that illustrated in Fig. 1; whereas if this double-throw switch DS is thrown to the opposite position the car-carried apparatus will comprise two receiving devices, one of which is adapted to pick up the current flowing in the loop circuit of an alternating current track circuit, that is, a current flowing in the opposite direction in the two rails, and the other receiving device being employed to detect the current flowing in the receiving circuit, or in the same direction in both rails in multiple.

The car-carried apparatus will first be described with the double-throw switch DS in the position illustrated, that is, for accomplishing train control in direct current block signal territory, such as the block I. The circuit for energizing the inducing elements IE may be traced as followsz-Beginning at the terminal 10 of the generator 9, wire 95, switch blade 96, to the generating or inducing bus IB, wire 97, switch blade 98, wire 99, coil 8 of the inducing element IE, wire 100, switch blade 101, wire 102 back to the inducing bus 13, to switch blade 103, wires 104 and 105 back to the terminal 14 of the alternating current generator 9; and a partial circuit also connected across the inducing bus IB, which may be traced as follows:-Beginning at the inducing bus 13, wire 106, switch blade 107, wire 108, coil'l45 8 of the other inducing element, wires 109 and 100, switch blade 101, wire 102 back to the inducing bus The flow of the current in the loop circuit, due to the induction elements IE, causes a current to through the transformer P, which in turn induces a voltage in the receiving elementsRE, which is impressed upon the amplifying device A. This circuit through the coils of the receiving elements RE may be traced as follows :Beginning at the inlet wire 31 of the amplifying device A, through the one wire of the receiving bus RB, wire 110, switch blade 111, wire 112, receiving coil 26 of one of the receiving elements RE, wires 113 and 114, coil 26 of the other receiving element, wire 115, switch blade 116, wire 117 back through the other wire of the receiving bus RB, to the other inlet wire 32 of the amplifying device A. A condenser 42 of the proper capacity is connected across the coils of the receiving elements for tuning purposes- The voltage induced in the receiving elements RE will cause a current to flow in the secondary field winding 57 of the relay R, thereby maintaining the relay energized in the direction as indicated in the drawings, the other or local field winding 60 of this relay R being energized by the alternating current generator 9 through the following circuit:Beginning at the terminal 10 of the generator 9, wire 95, switch blade 118, wire 119, local field winding 60 of the relay R, wire 120, switch blade 121, wires 122 and 105 back to the terminal 14 of the alternating current generator 9. I

With the relay R energized in the normal or clear traffic condition, as indicated in the drawings, a circuit for energizing the green lamp G may be traced as follows:Beginning' at the battery 125, wire 126, movable contact 127 of the relay R, stationary contact 128, a green or clear indication lamp G, wires 129 and 130 back to the battery 125.

Under this, the clear tramc condition, a circuit for energizing the cautionary train control device K will be energized through a circuit, which may be traced as followsz-Beginning at the battery 125, wire 126, movable contact 127 of the relay R, stationary contact 128, wire 131,

cautionary train control device K, wires 132, 133 and 130 back to the battery 125.

Under this same condition, a circuit may be traced through a danger train control device D, as followsz-Beginning at the battery 125, wires 126 and 134, movable contact 135, stationary contact 136, wire 137, danger train control device D, wires 138, 139, 133 and 130 back to the battery 125. Therefore, under the clear traflflc condition, both the cautionary train control device K and the danger train control device D will be energized, and the clear indication lamp G will be illuminated.

Operation.--Let us assume that a train equipped with the apparatus illustrated in Fig. 3 is moving in the block I with no other train ahead of it in said block, and also with the block J unoccupied, that is, is moving in block I under clear tramc conditions. Under this condition, the relay R will be energized with its movable contacts in the position illustrated in the drawings, thereby permitting the train to proceed without restriction substantially in the same manner as described in connection with the apparatus illustrated in Fig. 1.

Let us, now, assume that the block J is occupied when the train in question enters the block I. The presence of a train in the block J causes the alternating current track relay 5 to be deenergized, causing it to drop its front contacts 76 and thereby reversing the connections and the instantaneous polarity of the current in the receiving circuit. The reversal of the instantaneous polarity of the current in the receiving circuit relative to that of the alternating current generator 9, causes the torque produced by the relay R to be in the reversed direction, thereby swinging the movable contacts 127 and 135 to the other extreme position, thereby interrupting the circuits through the clear indicating lamp G and the cautionary train control device K, and completing a circuit through the caution indicating or yellow lamp Y. This latter circuit may be traced as follows:-Beginning at the battery 125, wire 126, movable contact 127, wire 140, caution indicating lamp Y, wires 141,142, 139, 133 and 130 back to the battery 125. This causes the train to be automatically controlled in accordance with the restriction of the cautionary train control device K, and advises the engineer that he is now occupying a caution block, this being manifested by the illumination of the yellow lamp Y and the extinction of the green lamp G. The required phase relation between the currents in the two phases of the relay R, for proper functioning of this device, may be obtained by adjusting the phase relation on the vehicle, or in each block along the trackway in any suitable manner as desired.

Let us, now, assume that the train in question is entering the block I when this block is occupied by another train. Under this condition, the transformer P will be deprived of the current flowing in the loop circuit because this current is now flowing through the axles of said another train ahead. Consequently, the generator 9 on the following train is unable to provide current for the receiving circuit, comprising the track rails 1 and 2 in multiple, which results in the deenergization of one field of the relay R, thereby causing its movable contacts 127 and 135 to assume their intermediate or neutral position due to the inherent bias of the relay, as common in relays of this type. At this position of the relay, both the cautionary train control device K and the danger train control device D, will be deenergized and likewise the clear or green lamp and the cauilin or yellow lamp, will be deenergized, and the red or danger lamp will be energized through a circuit, which may be traced as follows:-Beginning at the battery 125, wire 126, movable contact 127, stationary contact 143, red or danger lamp RL, wires 144, 142, 139, 133 and 130 back to the battery 125. This advises the engineer that he is now occupying a danger or occupied block.

It should be noted that the circuit for energizing the danger train control device D is momentarily interrupted during the time the relay R changes from its clear to its caution position. This momentary interruption of the circuit through this train control device D, however, may be made ineffectual by constructing this device to be slow acting to an extent to allow such movement of the relay from its one extreme to its other extreme position before said device operates effectively.

Let us, now, assume that under clear traflic conditions the vehicle, moving in block I with its train control apparatus in its normal condition. enters the block J. If the engineer does not operate the double-throw switch DS, the relay R will be deenergized. because the current induced in the loop circuit ahead of the train does not produce a corresponding current in the reenergized from the transmission line 82 ceivingcircuit, assuming the track transformer to have a relatively high reactance for the train control frequency. This deenergizes the cautionary train control device K and the danger train control device D, and further energizes the red or danger lamp RL and deenergizes the green lamp G, with the result that the engineer knows that either the block J has suddenly become a danger block or he has entered alternating currentblock signal territory. In other words, the relay R becomes deenergized, because one of the fields is energized by current from the altemating current generator 9, and the other field is If theengineer throws the double-throw switch DS to the dotted position and traflic conditions ahead in the block J and in the block K are clear,

the relay R will again be energized to its clear indicating position.

The circuit for energizing the phase winding 5'? ofthe relay R in an alternating current block, with the switch DS thrown to the dotted position, is the same as heretofore described and need not again be traced. The local phase winding of the relay R will under this condition be energized through a circuit, which may be traced as followsz-Beginning at the coil of one of the inducing elements IE, wire 99, switch blade 98, wire 9'7, inducing bus wire IB, switch blade 96, wire 150, through the amplifying apparatus A wire 151, switch blade 118, wire 119, local field winding 60 of the relay R, wire 120, switch blade 121,

wire 152 back through the amplifying apparatus.

1E; and in multiple with the coil 8 -just mentioned is a partial circuit through the other inducing element IE, which may be traced as follows:-Beginning at the inducing bus 13, wire 102, switch blade 101, wires 100 and 109, coil 8 of the other inducing element IE, wire 108, switch blade 107, wire 106 back to the inducing bus IB. In order to properly tune this circuit for the frequency employed condensers 123 and 124-have been provided.

The alternating current flowing down one rail 2 and back through the other rail 1 of the block J, as indicated by the solid arrows, which is derived from the transmission line 82 is therefore detected by the elements IE heretofore referred to as inducing elements, then amplified by the amplifying device A and transmitted to the field winding 60 of the relay R; whereas the current flowing in the same direction in the two rails 1 and 2, as indicated by the dotted arrows, is picked up by the receiving elements RE in back of the tender, then amplified and transmitted to the other field winding 5'7 of the relay R.

For an induction type relay, these currents preferably have their phase relation so adjusted that one of them lags substantially 90 electrical degrees behind the other. This may be accomplished by inserting resistance or inductive reactance in one of the phases, or it may be accomplished by transmitting polyphase currents along the trackway and by energizing the loop circuit by one phase of the polyphase transmission line source, and energizing the receiving circuit by another phase of said source of energy.

Let us, now. assume that this train enters the block J when the block K is occupied. The block K, now being occupied, causes the track relay 5 to be deenergized for reasons heretofore given, thereby reversing the polarity of the receiving car axle.

circuit heretofore traced. Since the. instantaneous direction of flow of current in the receiving circuit, as indicated by the dotted arrows,

is now reversed, it is obvious that the current fiowing in the field 57 of the relay Rwhich is due I to a current in the receiving track circuit, will also be reversed with respect to the current fiowing in'the other field 60 of this relay. Consequently, the torque produced by the relay R will be reversed, thus swinging the movable contacts 85 127 and 135 to the other extreme position. This will deenergize the green lamp G and the caution ary train control device K, and will energize the yellow or caution lamp Y for reasons described in detail in connection with the operation of the train control device in-the block I.

Let us, now, assume that the train enters the block-J when this'block is occupied by another train ahead. Under this condition, current will be flowing in the field winding 5'7 of the relay R due to current flowing in the receiving track circuit of the block J, and this current and its phase relation will depend on whether the block K is occupied or not. The phase relation of this current is, however, immaterial at this time, because the other field 60 of the relay R. will be entirely deenergized, because the current flowing in the loop circuit ahead of the train in question will not reach this latter train at all, but will flow through the axles of the train nearest the exit end 10,5 of the block J. The field 60 now being entirely deenergized will cause the relay R to assume its neutral or deenergized position, thereby deenergizing both the cautionary train control device K and the danger train control device D, and at the same time extinguishing the lamp G and illuminating the danger or red lamp RL.

Automatic reversing switch-In order to permit the vehicle, equipped with train control apparatus illustrated in Fig. 3, to move with either end leading or ahead, that is, if the equipment in question is mounted on a locomotive and tender, to permit this equipment to run either pilot or tender first, without duplicating the receiving apparatus, an automatic reversing switch has been provided which automatically changes the receiving elements RE to inducing elements and changes the inducing elements IE to receiving elements, changes in the coils being also made if found desirable. As shown, the receiving elements RE and the inducing elements IE are assumed to be identical in design, those mounted in front of the vehicle being connected in multiple and serving as inducing elements. whereas those mounted at the rear of the tender are connected in series and serve as receiving elements.

The automaticswitchoperator for actuating the switch blades 98, 101, 107, 116, 156 and 111 comprises a hub 15'! mounted on the axle 158 of the railway vehicle. This hub 15'! is provided with an extending arm 159 having a perforated lug 16') extend ng therefrom. A brake-shoe 161 provided with a rod 162 extending through the perforation of the lug 160 is provided, On the rod 162 between the brake-shoe 161 and the lug 160 is a spring 163 which u ges the brake-shoe 161 against the axle 158. thus providing frictional engagement between the arm159 and the By looking at the drawings, it is obvious that if the vehicle is moving in the normal direc ion of traffic from left to right. a indicated by the large arrow in block I, the axle will be turned clockwise, as indicated by the arrow 164, thus moving switch rod 165 to place it;

the switch blades 98, 101, 10'], 116, 156 and 111 moves in the opposite direction, these switch blades will assume the dotted position and complete the following partial circuits between the.

inducing and receiving elements IE and RE and the inducing bus and receiving bus 13 and RB, respectively. These partial circuits may be traced as followsz-Beginning at the inducing bus 1B, wire 166, switch blade 111, wire 112, coil 26, wire 113, wire 167, switch blade 156, wir'e 168; and another partial circuit as follows:-- Beginning at the wire 168, switch blade 156, wires 167 and 114, coil 26, wire 115, switch blade 116, and wire 169. The partial circuit connected to the receiving bus RB under this condition may be traced as follows:--Beginning at the wire 170, switch blade 107, wire 108, coil 8, Wire 109, other coil 8, wire 99, switch blade 98, and wire 171.

By studying the devices thus far described in connection with Fig. 3, it is apparent that, if the engine equipment employing the train control devices illustrated, is pushing a train ahead of it in the normal direction of traflic, with either the tender or the pilot leading, or if a train with the engine ahead as usual and running in the normal direction of traffic Should back up, in each of these instances on account of the operation of the automatic reversing switch,

the inducing elements IE for the system having a source of energy on the vehicle will be at that end of the locomotive where the cars that it is pushing are, therefore the energy supplied to the loop circuit will flow through the axles of said car and will not reach the transformer P to be transmitted into the receiving circuit. The same is true if a train, with the engine leading, should run in a direction opposite to the normal direction of trafiic. On the other hand, if the train is making such moves in a block, such as the block J, where the source of energy is located along the trackway, the inducing elements which now serve as receiving elements to pick up current flowing in opposite directions in the two rails, will be at the rear of the tender and will therefore be unable to pick up such current,

since this current will be shunted by the axles of the locomotive and tender.

In order that a locomotive may make the peculiar movements just discussed, that is, push a train ahead of it, back-up, or run against the normal direction of traffic in systems which are signaled for only one direction of traflic, means are contemplated to permit safe movement of the train faster than ordinarily allowed with the danger train control device D actuated or deenergized. Such means has been provided, as illustrated, by the release device RD. This release device RD is one which must be continuously operated by the engineer to permit him to proceed at a speed higher than that permitted by the danger train control device D. This release device RD comprises a hand or treadle operated centrifugal-switch, and has been illustrated as a spur gear 172 provided with a handle or treadle 173 pivotally mounted in any suitable manner and continuously in driving engagement with a pinion 174 keyed to a shaft 175. To this shaft is pinned a collar 183 which is mechanically connected to a shiftable disc 184 by links 185 and 186 having centrifugal weights 187 at their pivotal connection. The disc 184 is held away from the collar 183 by a compression spring 188. Adjacent the disc 184 is a stationary contact 179,

and a movable contact 178 having an insulating tip 189. Upon rotation of the shaft 175 the force, due to the centrifugal action of the weights 187, causes the disc 184 to slide sidewise and complete a circuit between the movable contact 178 and the stationary contact 179.

Let us assume, now, that the engineer is making a back-up move, or is moving against the normal direction of traffic. Such movement of a train is usually carried out'by the authority of written train orders. As soon as such a backup move against the normal direction of traflic is made, the relay R will be deenergized for reasons heretofore stated, thereby limiting the speed or movement of the train in accordance with that permitted by the danger train control device D. If the engineer wishes to proceed, only restricted by the cautionary train control device K, he may do so by giving evidence of the fact that he is awake and aware of traflic conditions similar to danger trafiic conditions, by actuating the crank or treadle 173. The actuation of this treadle or crank 173 at a predetermined rate operates the shaft 175 at a speed to cause the centrifugal weights 187 to move further apart, thereby sliding the disc 184 toward the collar 183, thus urging the movable contact 178 against the stationary contact 179. -This will complete a circuit, which may be traced as follows:--Beginning at the battery 125, wires 126 and 134, movable contact 135, stationary contact 180, wire 181, movable contact 178, stationary contact 179, wires 182 and 137, danger train control device D, wires 138, 139, 133 and 130 back to the battery 125. The completion of this circuit energizes the danger train control device D, and permits the engineer to proceed restricted only by the cautionary train control device K.

Let us assume, now, that the engine and tender equipment is turned around, and is therefore running tender first in the direction of tramc. Under this condition, the automatic reversing switch will be moved to the dotted position, thereby changing the circuit connections to connect the inducing elements IE in series and the receiving elements BE in multiple, thereby connecting the leading elements which are located on the rear of the tender to the alternating current generator 9, and connecting the trailing elements mounted on the pilot end of the engine for detecting currents flowing in the same direction in the running rails, assuming direct current block signal territory, thus allowing the engineer to proceed in accordance with trafilc conditions. The conditions, when moving in alternating current block signal territory, will be obvious to those skilled in the art from the discussion of the relation of the several devices, depending on the position of the double-throw switch DS as heretofore described.

It should be understood that if two-condition train control is to be accomplished with the apparatus illustrated in Fig. 3, that this may be done by substituting a simple single front con-' tact for controlling the receiving circuit, for the double-pole double-throw contact actuated by the track relay 5, similar to the arrangement illustrated in Fig. 1. In practicing the invention as just described in connection with Fig. 3, although the frequency of the carcarried generator may 1 be the same as the alternating current signaling frequency, it is preferably different, and adjustable tuning devices are preferably employed to tune to this frequency or the commercial frequency.

Description of Fig. 4.-In Fig. 4 has been illustrated a modified form. of the invention shown and described in connection with the block I of Fig. 3. The principal distinction of this embodiment over the one just described, is that the energy is transmitted from the train carried source to the transformer P located at the exit end of a block by an independent and insulated circuit, which for convenience will be called an inducing circuit, and the energy is picked up from the loop circuit comprising the track rails 1 and 2 ahead of the train. This inducing circuit may be traced as follows:--Beginning at the inducing wire 200, wire 201, stationary contact 202 front contact 203 wire 204, winding 1'7 of the transformer P, wire 205, front contact 206 stationary contact 207 line wire 208 back to the inducing wire 200.

In this form of the invention only a single inducing element IE is provided. This element IE, as shown, comprises a U-shaped laminated core 209 terminating in pole pieces 210 and having a coil 211. This inducing element IE is designed and constructed to properly cooperate with the inducing wire 200 and may have only a small air gap between the pole pieces 210 which must be traversed by the magnetic flux necessary to induce the desired voltage in the inducing circuit. This inducing element is energized by the alternating current generator 9, through a circuit which may be traced as followsz-Beginning at the terminal post 10 of the alternating current generator 9, wire 212, coil 211, wire 213 back to the other terminal 14 of the alternating current generator 9. This inducing circuit is preferably entirely insulated from the track circuit. Various arrangements for supporting the inducing wire along the trackway may be employed, for instance, a channel-like trough may be laid either between the rails or on the outside thereof and upon the ties for carrying a bare or weather-proof insulated wire over which an inducing element IE is adapted to pass, or a third rail or" small cross-sectional area and preferably made of non-magnetic material may be used.

The local field winding of the relay R is energized v by the alternating current generator 9, through a circuit which may be traced as follows:-Eeginning at the terminal 10 of the generator 9, wire 21,-local field winding 60 or" the relay R, wire 215 back to the terminal 14 of the alternating current generator 9.

The secondary field winding 57 of the relay is energized by the coils 26 of the receiving elements RE and the amplifying device A, through a circuit which may be traced as follows:-Beginning at the coil 26 of one of the receiving elements RE, wire 216, coil 26 oi" the other receiving element, wire 217, through the amplifying device A, wire 218, secondaryfleld winding 5'? of the relay R, wire 219 back through the amplitying device A, wire 220 back to the coil 26 of the receiving element RE.

The devices controlled by the relay R are substantially the same as those described in connection with Fig. 3, and will therefore be given the same reference characters. Since the operation of this embodiment of the invention is substantially the same as that described in connection with Fig. 3, a description thereof is deemed unnecessary and will be omitted.

Description of Figs. 5, 6 and 7.-In Figs. 5, 6 and '7 have been illustrated several modified forms of inducing and receiving devices adapted for us in connection with trackway circuits, such 'vehicle equipped therewith to be in the direction as illustrated in Figs. 1 and 3. The principal distinction of these modified forms of devices from those illustrated in Figs. 1 and 3, is that the receiving devices or elements RE are connected to detect or receive currents flowing in opposite directions in the running rails of the trackway, similar to the receiving elements RE illustrated in Fig. 4; and the inducing devices or inducing elements IE are designed and constructed to induce currents in the same direction in both of the track rails in multiple, which, by the aid of a return line wire and a transformer are adapted to produce current in the loop circuit comprising the usual track circuit.

In Fig. 5 such communicating devices, that is, devices in which current is induced in a circuit including both of the track rails in multiple, and in which current is detected in the loop circuit ahead of the train in a block, have been illustrated so that they may be substituted in the system illustrated in Fig. 3. In order to simplify the explanation of how the devices illustrated in Fig. 5 may be substituted for the inducing and receiving elements, shown in Fig. 3, the same reference characters, namely, 99, 100 and 108, and 112, 167 and 115 have been assigned to the six lead-in wires of both of these sets of devices.

In this arrangement of communicating devices, assuming the direction of movement of the of traiiic, as indicated by the arrow DT, the inducing elements IE, which are assumed to be the same in construction as the receiving elements but are merely connected for inducing purposes while the train is moving in that direction, are energized by the generator 9, as is obvious when tracing the energizing circuit in Fig. 3 in connection with the lead-in wires 99, 100 and 108 of Fig. 5. Under this condition, the traffic controlled reversing switch- BS is in the position as indicated in Fig. 3.

Current flowing in the circuit through the inducing elements IE just mentioned, will-induce a voltage in the same direction in both of the running rails at a point between the tender, as

diagrammatically indicated by the wheels and axle 221, and a trailing train as diagrammati cally indicated by the wheels and axle 222. It is apparent that, if such voltages are induced in the track rails between said tender and trailing train, a current will how in a local circuit comprising the two rails in multiple, the wheels and axle of the tender 221, conducting connections between the tender and train, shown as coupling bars 223 and 224, wheels and axles of the trailing train 222 back to the track rails. Various expedients may be employed to prevent such new of current in the local dissipating circuit just mentioned, for instance, the coupling bar 223 may be insulated from the tender and other 35 voltage into the coupling bar and other connec;.l40

tions, which is substantially equal to the voltage induced in the track rails and in the same direction with respect to said track. Means for inducing such a voltage in the coupling bar 223- has been provided by mounting a closed lami- 14 nated core 225 on the rear end of the tender 221, through which the coupler or drawbar 223 and other devices connecting the tender with the trailing train pass. On this core 225 is provided a coil 226 which is connected in series with the wire 100, therefore causing the current flowing through the coils of the inducing elements IE to flow through the coil 226 of the inducing transformer IT formed by this coil and the core 225. The several devices are designed with relation to each other, so that the voltage induced in the track rails and the voltage induced in the coupler bar 223 are substantially the same. This construction, therefore, induces a voltage in the train and in the track, so to speak, which produces a flow of current in the winding 17 of the transformer P at the exit end of the block I (see Fig. 3), assuming the vehicle so equipped to be moving in this block. The other winding 15 of this transformer P will in turn cause a current to flow in the loop circuit ahead of the train, which current will be detected by the receiving elements RE in front of the locomotive, as conventionally illustrated by the wheels and axle 228. The manner in which the train may, be controlled by the current thus picked up from the loop circuit is obvious from the illustration and description of Fig. 3.

It should, however, be noted that the receiving elements RE and the inducing elements IE are used for inducing purposes when the train is.

moving in a direction to place them at the rear end, and are used for receiving purposes when the vehicle is moving in a direction to place them on the front end thereof. Further, when one of these sets of devices is used for inducing purposes, the inducing elements IE are connected in multiple with each other and in series with the inducing transformer IT, in a manner so that a voltage is induced in the two rails in multiple and coupling bar in the same direction; and when connected for receiving purposes are connected in series so as to detect current flowing in the opposite direction in the two track rails, leaving the inducing transformer IT associated therewith in an open circuit. The inducing transformer IT, located in front of the locomotive 228, is positioned so that the auxiliary coupler bar 227 passes through the core 225 of this transformer.

If a train control system, such as illustrated in Fig. 3, is desired, with the exception that it is preferred to induce current into the two rails in multiple, and in turn detect signaling and control current from the loop circuit ahead of the train, this may be accomplished by substituting the inducing and receiving devices shown in Fig. 5, bearing of course in mind that the several devices must be designed with respect to each other for such use.

The inducing and receiving devices illustrated in Fig. 6 function substantially the same as those illustrated in Fig. 5, that is, they induce voltages in the same direction in the two rails in multiple, and detect the flow and character of the current flowing in the loop circuit ahead of the train. The principal departure consists in providing for the inducing element a single U-shaped core similar to the receiving elements RE illustrated in'Fig. 2, only that this inducing element is sufficiently long to bridge both of the track rails, and is located in front of the locomotive or vehicle, as represented by the axle and wheels 228 This inducing element IE comprises a long U-shaped laminated core 229 provided with a winding 230, preferably extending entirely along the back yoke and along the legs formed by this core. In this form of the invention, no local dissipating circuit is present, since the inducin is accomplished ahead of all the axles: and

on the same core structure.

therefore the additional inducing transformer IT illustrated in Fig. 5 is unnecessary.

In Fig. '7 has been illustrated still another form of inducing and receiving apparatus. In this embodiment of the invention, both the inducing winding .and the receiving winding are mounted This combined inducing and receiving element IRE comprises a back yoke 232 having three downwardly extending legs 233, 234 and 235, respectively. These legs terminate in suitable pole pieces 236. The outside legs 233 and 235 and the back yoke 232 are provided with an inducing winding 237, which, if energized by alternating current, causes an alternating flux 'to link about both rails of the trackway, thereby inducing voltage in both rails in the same direction. The voltage induced in the track rails in this manner may be utilized to energize a transformer at the exit end of the block which will induce a current in the loop circuit ahead of the train, that is, will induce a current flowing toward the train in one rail through the axles of the train back through the other rail to the transformer just mentioned. The alternating current induced in the loop circuit in this manner will cause an alternating magnetism to be set up in the inducing and receiving element IRE through the following partial magnetic circuits, one of which comprises the leg 234, one half of the back yoke 232 and the outside leg 235, and another partial magnetic circuit comprising the middle leg 234, the other half of the back yoke 232 and the other outside leg 233. It is thus seen that substantially all of the magnetism flowing in the inducing and receiving element IRE, due to the current flowing in the loop circuit, passes through the middle .leg 234, whereas very little flux passes through this middle leg due to the current flowing in the winding 237. It is, therefore, apparent that the voltage induced in the coil 238 surrounding the middle leg 234 may be amplified and transmitted to the secondary winding of the relay R heretofore described to control the train in a manner dependent on traffic conditions in advance.

If it is desired to use the inducing and receiving devices illustrated in Figs. 6 and 7 for double end equipment, that is, so that either end of the vehicle equipped may run ahead, duplicate inducing and receiving devices,.such as shown, may be mounted on the opposite ends of the vehicle. To throw either of these devices into service, depending on the direction of movement, a fourpole double-throw switch may be provided, of which the blades are connected to the inducing bus 13 and the receiving bus RB illustrated in Fig. 3, respectively, and of which the stationary clips on one side of the switch are connected to the proper lead-in wires of one of said devices, and of which the stationary clips on the other side of the switch are connected to theother of said devices; whereby if the switch is thrown one way, one of these devices will be cut into service,

and if the switch is thrown the other way, the I other device will be cut in.

Structure of Fig. 8.--In Fig. 8 has been illus- In this form of the I said rails, thus "causing a current to flow in the loop circuit ahead of the train either through an inductive reactance 240 or an ohmic resistance 241, depending on traffic conditions in the blocl; ahead.

While various devices maybe employed for detecting or receiving currents responsive to current flowing in the loop circ 't ahead of the train as already described in connection with previous forms of this invention, still another means for this purpose is used in Fig. 8. It has been found in practice that a large percentage of the'current flowing in the track circuit shunted by a train flows through the wheels and axles of the first truck of the train. It has, therefore, been proposed to provide means for detecting the flow of current through one or more of the axles of the first truck of the train by the well-known transformer principle, this principle being especially well adapted for this purpose. This axle transformer AT has bmn illustrated by a core 242 constructed of a high grade of laminated transformer iron and provided with a secondary coil 243, the primary winding of the transformer consisting of a single turn which comprises the car axle itself. The presence of the current in the loop circuit and its phase relation with respect to the voltage generated by the polyphase alternating current generator 244 is preferably ascertained by the employment of a phase responsive relay PR, which will precisely indicate the phase relation between two alternating currents. Such a phase responsive relay PR has been conventionally shown, and comprises a stator similar to that of a polyphase induction motor and a rotor having a single or polyphase winding.

The phase responsive relay PR more specifically comprises a stator having a three-phase winding, as indicated by the coils 245, 246 and 247, this stator winding being directly energized through the lead-in wires 248, 249 and 250 leading to the three terminals of the polyphase alternating current generator 244. Within the stator is pivotally mounted a rotor which is provided with a single phase winding 251 to be connected to the source of alternating current voltage, the phase relation of which, with respect to that of the phase relation of the voltage impressed on the stator, is to be determined. This rotor winding 251 may surround an iron core, but if such an iron core is employed, the construction should be such that practically no turning moment will produced if the stator only is energized. This may be done by mounting a stationary core within the stator about which the winding 251 is adapted to rotate. The circuit controller adapted to be actuated by this phase responsive device has been conventionally shown to illustrate how this device may be constructed so as to maintain a circuit closed when a certain predetermined range of phase displacement exists between the voltage impressed on the rotor winding and the voltage across any one of the phases of the stator winding.

This circuit controller comprises a disc 25% fastened to the relay shaft 252. This shaft 252 and disc 254 are biased to a deenergized position by a hair-spring 253, this position being shown in dotted lines. The disc 254 is provided with a pin 258 adapted to engage the movable contact 256. With the relay energized to a position such as the position illustrated in the drawings, the movablecontact 256 will be held in engagement with the stationary contact 257 by a spring 255. The hair-spring 253 is, however, strong enough to open the contacts 256-257 against the tension' of the spring 255 when the phase relation of thecurrents is such as to allow the pin 258 to strike the movable contact 256.

If now the relay PR is energized by current having a predetermined range of phase relation, the disc 254 will be brought to a position, such as the position indicated in the drawings, thereby allowing the spring 255 to bring the contact finger 256 against the stationary contact 257. If now the phase relation changes to move the disc toward the dotted position, nothing happens until the pin 258 strikes the contact finger 256 and urges it away from the stationary contact 257 against the tension of the spring 255. Consequently, if for any reason the phase responsive relay PR is deenergized, the hair-spring 253 will overcome the tension of the spring 255 to interrupt a circuit adapted to 'be completed through the movable contact finger 256 and stationary contact 257. In practice the movable element of this relay is preferably well balanced, and is also preferably supported in a heavy spring supported casing, so that its operation will not be affected by jars and vibration. The circuit for energizing the rotor winding251 of the phase responsive relay PR may be traced as iollows:-- Beginning at the secondary winding 243 of the transformer AT, wire 259, inlet wire 32 through the amplifying device A, outlet wire 59, wire 260, winding 251 of the relay PR, wires 261 and 55 back through the amplifying device A, wires 31 and 262 back to the secondary winding 243 of the transformer AT.

A condenser 263 connected in multiple with the secondary winding 243 of the axle transformer AT, which is tuned to resonance with this winding 243 at the frequency at which the device is to be operated, is provided in order to improve the efiiciency and operating characteristics of the apparatus. A similar condenser 264, similarly adjusted with respect to the winding 251 of the phase responsive relay PR, is provided.

Operation 0 Fig. 8.-Let us assume that a railway vehicle equipped with the car apparatus illustrated in Fig. 8 is moving in a block, such as the block I, under normal clear traific conditions, that is, with the portion ahead of the train in the block I as well as the block J unoccupied. Under this condition, the track relay 5 will be energized, thereby including the inductive reactance 240 in the track circuit of the block I. The inducing or generating elements E are connected across the terminals of the polyphase alternating current generator 244 through a circuit which is obvious from the drawings. The alternating flux around the track rails, due to the exciting current flowing in the coils 6 of the inducing elements IE, will cause a current to flow in the loop circuit ahead of the train which lags considerably behind the voltage pro-- ducing it. This lag in the iiow of the current in the loop circuit is mainly due to the inductive reactance 2'40, and is also partially due to the reactance of the track rails themselves.

S nce a large percentage of the current flowing in this loop circuit passes through the axles of the front truck of the train, an alternating magnetic flux will be set up in the core 242 of the axle transf rrmer AT, thereby producing an alternating current voltage in the secondary coil 243 thereof. This voltage is impressed on theamplifying device A, whereby it 'is amplified and transmitted to the rotor winding 251 of the phase responsive relay PR through the circuit heretofore traced.

The flowof this current in the rotor winding acts on the rotating magnetic field produced by the stator winding to actuate the disc 254 against the action of the hair-spring 253 to a position dependent on the phase relation of this current to that of the voltage impressed on the stator windings, which may be assumed to be the position illustrated, thereby maintaining the movable contact finger against the stationary contact to complete a circuit through the train control device K, which is obvious from the drawings. The energization of this circuit will allow the train to proceed unrestricted by the automatic train control apparatus.

Let us assume, now, that the block J is occupied by another train which will shunt the usual track circuit currentof the block J through the wheels and axles of said train, thereby deenergizing the track relay 5 thus causing it to drop its makebefore-break contact 265 During this dropping of the contact 265 the track circuit of the block I will not be momentarily interrupted, because the back contact will make the circuit through the ohmic resistance 241 before the front contact will break the track circuit through the inductive reactance 240. The track circuit of the block I has now been changed to a circuit which comprises to a large extent an ohmic resistance, because the inductive reactance 240 has been omitted. In ractice the ohmic resistance of inductive reactance 240 is made substantially the same as the resistance 241, so that the direct current constants will be the same in each case. The alternating current now flowing in the loop circuit of the block I is much nearer in phase with the voltage producing it, or in other words, the current flowing is to a large extent ohmic or a power current.

This current will be transformed, amplified, and

transmitted to the rotor winding 251 of the relay.

PR, in the same manner as heretofore explained in connection with the reactive current produced in a clear block. With this current flowing in the rotor winding 251 of the relay PR, the disc. 254 will assume a position which, as before, is dependent on the phase relation of this current to that of the currents flowing in the stator winding, and is substantially independent of the value of this current itself, for instance, such as the dotted position illustrated, thereby causing the pin 258 to strike the contact finger 256 and open the circuit through the train control device K.

The deenergization of the train control device K will enforce a speed restriction or other control dependent on the design and construction of this device. This device is preferably of a character to compel a reduction in speed until a final low speed limit is .reached, which will be enforced until a clear block is entered, or until the block in which the restricted train is running clears up.

Assuming, now, that a train equipped with the apparatus in question is entering the block I under danger tramc conditions, that is, when the block is occupied by another train. Under this condition, the loop circuit ahead of the train is also resistive to a large extent, regardless of whether the track relay 5 at the entrance of the block J is energized or deenergized, because this loop circuit is completed through the wheels and axles of said another train ahead of the train in question. The current transformed, amplified, and transmitted to the rotor winding 251 of the phase responsive relay PR under these conditions -will be substantially the, same as under caution traffic conditions, as explained in the preceding paragraph; and since in both instances the loop circuit is only slightly inductive, the train will. be

restricted in its movement in the same manner as under caution traffic conditions.

Description of Fig. 9.--In practice it has been found that many of the important railroads have a large portion of their roadway provided with direct current block signaling equipment including direct current track circuits, but that at local points in such sections a few blocks of alternating current track circuits are often employed. This is usually because local conditions make the use of direct current circuits unreliable on account of the presence of stray direct current flowing in the track rails. Such currents are usually due to bad bonding on other parallel railroads using direct current for traction purposes. Further, it is also found that some of the important railway systems are partially electrified, and are using direct current for propulsion purposes which also requires the use of alternating current track circuits for governing wayside signals, and the like. In order to facilitate train control on railroads of this kind, it has been proposed to superimpose suitable trackway devices and circuits, on both direct current and alternating track circuit territory, which, although different in character, will adapt them for the track circuit with which they are used without interference, and will affect suitable car-carried train control apparatus in accordance with traffic conditions ahead.

It is proposed in the present embodiment to transform relatively high frequency alternating current into the loop circuit of a direct current track circuit by connecting the secondary of a transformer in series with the usual track battery; and to transform similar high frequency alternating current into an alternating current track circuit by connecting a transformer having a current limiting device in series therewith which is tuned to resonance at said relatively high frequency inmultiple with'the usual track circuit transformer. This arrangement of connections in alternating current track circuits will permit such high frequency current to pass through said current limiting device, but will not let an alternating current of commercial frequency pass therethrough to any appreciable extent; and on the other hand, the high frequency alternating current will not be able to pass through the secondary winding of the track-circuit transformer to any appreciable extent, because of the high value of self-induction of this secondary at such a high frequency.

One of each of said types of trackway circuits has been illustrated in Fig. 9, one of which is adapted to be superimposed on an alternating current block signal system, such as the blocks H and I shown, and the other to be superimposed on a direct current block signal system, similar to the block I shown in Fig. 3, as shown by the blocks J and K. These trackway circuits are so constructed that a vehicle equipped with the inducing and receiving apparatus, such as illustrated in Figs. 3, 5, 6 and 7, may induce and also detect current independently of the direct current or alternating current track circuit current flowing, and control the train according to the relative instantaneous polarity of the current detected with respect to'the instantaneous current supplied by the alternating current, generator carried by the railway vehicle. This is because the alternating current detected must be of the same frequency and of a certain phase relation within certain limits to that of the our- 156 rent impressed on the other phase of the relay R as illustrated. The blocks H and I are of a type employing an alternating current in their track circuits, as illustrated by the alternating current track relay 281 at the entrance of block I, and a trackway transformer TT supplied from an alternating current transmission line 282 provided at the exit end of said block.

In the block I has been shown an inducing circuit, which may be traced as follows:Beginning at the track rails 1 and 2 in multiple, to the middle point of the balancing resistance BR at the entrance of the block, line wire 266, stationary contact 267 movable contact 268 wire 269, primary winding 270 of the transformer P, wire 271, movable contact 272 stationary contact 273 wire 274 to the middle point of the balancing resistance BR located at the exit end of the block I, back to the track rails 1 and 2.

The induction of an electro-motive-force in this inducing circuit will cause a current to flow in the loop circuit including the secondary of said transformer P, which circuit may be traced as followsz-Beg-inning at the secondary winding 2'75 of the transformer P, wire 276, condenser 2'27 in multiple with the adjustable inductive reactance 278, wire 279, track rail 1, through the axles of the train occupying the block I at this time, through the rail 2, wire 280 back to the secondary winding of the transformer P.

Under clear traffic conditions of the block I, a train equipped with the apparatus heretofore described, and provided with inducing and receiving elements, such as shown in Figs. 5, 6 and 7, will induce a current in the inducing circuit which will be transformed by the transformer P in the loop circuit ahead of the train. The voltage impressed across the track rails 1 and 2 of the loop circuit will permit very little, if any, current to flow in the local circuit completed by the usual trackway transformer T1, because the self-induction of a trackway transformer of this type which is designed for commercial frequencies has suflicient self-induction to prevent the flow of alternating current of a relatively high frequency therethrough. On the other hand, the secondary winding 2'75 of the transformer P will permit very little, if any, current from the trackway transformer IT to flow therethrough, because it has connected in series therewith a current limiting device, comprising a condenser 27'? shunted by an adjustable inductive reactance 2'73 which has been tuned to resonance to the relatively high frequency by the generator carried by the railway vehicle. Since a current of high frequency may be induced in the loop circuit of an alternating current'trackway circuit as illustrated and described, it is apparent that automatic train control may be carried out in the same general way as heretofore shown and described in connection with direct current track circuit territory, therefore facilitating train control in a composite system where both direct current and alternating current track circuits are employed.

In the block J of Fig. 9 has been illustrated trackway equipment for facilitating automatic train control in direct current track circuit territory, which equipment functions the same as that described in connection with Fig. 3, and therefore need not be specifically described. The parts and circuits at the junction of blocks J and K of Fig. 9 have as a matter of convenience been given the same reference characters as the corresponding parts and circuits at the junction of blocks I and J of Fig. 3, except that the exponents of the reference characters 'are one number higher.

While different specific detail arrangements and constructions of devices and circuits have been illustrated and described in order to explain the characteristic features of the inventio it should be understood that the invention is not limited solely to these specific organizations, and that certain characteristic means and functions used in one. embodiment are .adaptableand are intended to be used in connection with other embodiments where it is desired to take advantage of the additional features provided thereby. Also, in order to avoid unnecessary complication in the description and explanation, many things concerning the detailed design and manner of practicing the invention have notv been described in full detail, it being considered that one skilled in the art will adapt and modify the size and shape of cores, windings, frequencies, etc., as may be desirable to best meet the individual conditions under which an installation is to be made.

Regarding the frequency, as previously stated,

it is considered preferable in most instances to V employ a relatively high frequency, subject to the limits imposed by the reactance of the track rails themselves, Furthermore, in order to avoid any possible interference between the signaling current produced on one train or vehicle with the receiving equipment by another train or vehicle and perhaps under unfavorable conditions produce an improper control between trains, it is contemplated that the inducing and receiving equipment of each train will be designed or adjusted for one particular frequency distinctive from the signaling frequency of all other trains. By carefully tuning the receiving equipment in the manner well-known in the art, it can be assured that this receiving means will not be influenced by a signaling current other than that produced on that train itself. Similarly, while one specific arrangement of amplifying means has been shown and described as typical of that employed in connection with this invention, it should be understood that this is also susceptible of considerable adaptation and modification in practice. In short, the various elements of the different specific forms of systems shown, such as the inducing elements and receiving elements, amplifying means, changeover switches and devices and the like, are capable of re-organization or re-arrangement to produce the particular character of system desired. Consequently,-any particular combination or arrangement of parts, or electrical structures, should not be excluded from the scope of this invention merely because they have not been individually shown or described.

Means have been provided by this invention for facilitating automatic train control which is continuous in its functions, thereby apprising the engineer and controlling the train automatically the moment a dangerous trafiic condition is engineer and due to danger present, and further advises the removes the restriction enforced traffic conditions the moment such danger traffic conditions are removed. Further, such an automatic train control system has been provided which will function equally as well in direct current track circuit territory as it does in alternating current track circuit territory, and per-v mits either end of the vehicle to run ahead without adding duplicate equipment for this purpose.

Q at the exit end of each block, and car-carried A train control system has thus been provided which does not require the transmission of current along the trackway from a source of energy on the ground, which current is unreliable and often fails along a long stretch of track, thereby removing all automatic protection which it otherwise affords. In the present system, if the source of energy should fai-l, it affects the particular train upon which the breakdown occurs; and on the other hand, if a line circuit or other track equipment cooperating with this train control system should fail, only that particular block in which it is located is affected. It is thus seen that in the event of a breakdown, whether on the car-carried apparatus or the trackway equipment, it is local in character, that is, it affects either a single train or a single block; whereas if alternating current transmitted by a long transmission line is relied upon, a large section of the system is very apt to be disabled at one time.

Having thus shown and described several embodiments of the present invention, it should be understood that many other arrangements of devices may be employed which have not been specifically illustrated, for instance, each of the modified forms of the inducing and receiving elements illustrated may by proper design be employed in any one of the systems shown and described; and we desire to have it understood that various obvious changes and adaptations may be made without departing from the spirit and scope of this invention.

What we claim is:--

1. In an automatic train control system of the type in which a control influence of the proper character must be present to allow the train to proceed unrestricted, of means carried by the train for producing a flow of current in the usual track rails ahead of the train at the particular time, said current flowing from a point at a distance ahead of the train through the track rails in opposite directions, and means on the train governed by said current for controlling the movement of said train.

2. In an automatic train control system of the type in which a control influence of the proper character must be present to allow the train to proceed unrestricted, of means carried by the train for producing a flow of current in the usual track circuit occupied by the train at the particular time, and means on the train jointly governed by currents so produced in said track circuit and said first mentioned means directly for controlling the movement of said train.

3. In an automatic train control system of the type in which a continuous control influence is necessary to allow the train to proceed unrestricted, of car-carried means for inducing an alternating current in a circuit including the track rails ahead of the train, said current flowing from a point at a distance ahead of the train back to the train through the track rails in opposite directions, and a train control device on the car maintained inactive by the current in said circuit.

4. In a train control system for railroads having tracks divided into blocks, a transformer having its secondary connected across the track rails means including a source of current on the car and a circuit on the trackway for-supplying alternating current from said car-carried source to the primary of the transformer 01 a given block at all points in the travel of the car through that block.

5. In an automatic train control system of the continuous inductive type, the combination of car-carried alternating current apparatus for inducing alternating currentin a circuit comprising the two track rails in multiple and a return wire, means whereby the current in said circuit produces an alternating current in the usual track rails ahead of the train flowing in opposite directions therein under clear traffic conditions, and means for maintaining a train control device in active only so long as there is current of a predetermined character flowing in one direction in one rail and in the other direction in the other rail directly in front of the train.

6. In an automatic train control system in which a continuous influence of a predetermined character must be transmitted from the trackway toa suitable car-carried apparatus to allow the train to proceed without restriction, of means partly on the vehicle and partly along the trackway for transmitting alternating current to a translating device located along the trackway, trafiic controlled means for energizing a track circuit including both of the running rails by said translating device in a plurality of difierent ways, and car-carried train control means maintained inactive by current of a predetermined character in said track circuit.

'7. Influence communicating means for train control systems comprising, car-carried means for inducing an alternating current in a circuit including the two rails in multiple, and means for detecting a corresponding current in a circuit including the two rails in series.

8. In a train control system of the continuous inductive control type and adaptable for con trolling trains on railroads having territory equipped with direct current track circuits and other territory equipped with alternating current track circuits, the combination of means on a car for inductively detecting the flow of alternating current in opposite directions in the track rails directly ahead of the car such as flows in the alternating current track circuits, and means for producing a similar alternating current-from a car-carried source in the track rails of each block having a direct current track circuit.

9. A train control system of the continuous inductive type comprising, receiving coils at different points on a locomotive for detecting the flow of alternating current in the track rails in opposite directions and in the same direction respectively, electro-responsive means on the 1000- motive having two input circuits, and automatic means having its operation dependent upon the direction of rotation of the locomotive wheels for interchanging the connections between said receiving coils and said input circuits as the locosaid two detecting means with respect to the circuits of the car equipment when the direction of movement of the vehicle changes.

11. In a train control system comprising, means for detecting the flow of alternating current in the same direction in both track rails at one end of a locomotive equipment, means for detecting the flow of alternating current in opposite directions in the two rails at the opposite end of said equipment, train control means governed by said currents, and means for electrically interchanging said two detecting means,

12. An automatic train control system comprising, automatic train control means, means for energizing said automatic means to maintain it inactive, and means for removing the restriction of said automatic means when deenergized which requires continuous movement by the operator to maintain it effective.

13. A device for reducing the restriction imposed by an automatic train control device comprising, apparatus adapted to be operated by the engineer which will remove such restriction when.

and only when said device is maintained in motion.

14. Influence communicating devices for automatic train control systems comprising, a carcarried alternating current device for inducing alternating current in a track circuit, a train control device maintained inactive by the current in said circuit if said current has a proper and predetermined phase relation with the voltage of said alternating current device, and traffie controlled means on the trackway for changing said phase relation.

15. In an automatic train control system for railroads having tracks divided into blocks each having the usualtrack circuit, the combination with a circuit on the trackway associated with each block, car-carried devices including a source of alternating current for inducing alternating current in said circuit on the trackway, automatic means controlled by the track circuit of the block next in advance for supplying current from said trackway circuit across the track rails at the exit end of each block, and car-carried means inductively influenced by the current in the track rails directly ahead of the car which flows in opposite directions, said car-carried means having a tendency to assume its active condition and being maintained inactive only so long as said current influencing it is flowing.

16. In an automatic train control system of the type in which a continuous influence of a predetermined character must be transmitted from the trackway to suitable car-carried apparatus to allow the train to proceed without restriction, of car-carried means including a source ofalternating current for energizing the usual track circuit including the track rails in advance of a train in question with alternating current flowing in opposite direction in said track rails, and other car-carried means for detecting by induction the presence and character of the current produced by said source and flowing in said track circuit.

17. In an automatic train control system for railroads provided with blocks each having a track circuit, two circuits on the trackway for each block and each including in part the track rails of that block, means controlled by the track circuit of each block for controlling the electricalconnection between said two circuits of the block next in the rear, car-carried means including a source of alternating current for inducing current in one of said trackway circuits at all points in the travel of the car through the corresponding block, and other car-carried means for inductively detecting the flow of current in the other of said trackway circuits.

18. In a train control system for railroads, the

combination with a section of track, a trackway circuit for supplying signaling current to the track rails of said section at the exit end thereof, said signaling current flowing in opposite directions in the track rails, means on the car for detecting the flow of signaling current in the track rails directly in front of the car, and means including a car-carried source of electrical energy for inducing signaling current in said trackway circuit at all. points in the travel of the car through said track section.

19. In a train control system, the combination with a section of track, a transformer having one winding connected across the track rails of said section at the exit end thereof, a circuit along the trackway for supplying current to the other winding of said transformer, and means on the car for inducing current in said circuit from a car-carried source of electrical energy at all points in the travel of the car through said section.

20. The method of communicating control influences for train control systems from the trackway to moving trains in accordance with traflic conditions which consists, in producing in the track rails ahead of a-train a signaling current derived from a source on that train, controlling this signaling current in accordance with the extent of unoccupied track in advance of said train,

transmitting said signaling current so controlled train for the purpose of governing cab signal or a train control mechanism upon that train in accordance with tramc conditions in advance thereof which consists, in producing in a trackway circuit by induction a signaling current derived wholly from a source of energy on the train, controlling said signaling current in accordance with the extent of unoccupied track in advance of said train, and transmitting said signaling current so controlled by induction to said train and there detecting its existence and character.

22. The method of continuously communicating control influences to a railway train dependent upon the presence or absence of another train on the track rails in advance thereof which consists, in producing in said track rails by induction from a source of energy on the train an alternating signaling current flowing in opposite directions at any instant in the track rails so as to be shunted by the wheels and axles of another train ahead of said train, and detecting by induction through an intervening air gap the flow of signaling current in the track rails adjacent to said train.

23. The method of continuous control for cab signal and train control systems which consists, in inducing from a car-carried source of energy an alternating signaling current which flows in a loop circuit from a distant point ahead of the" car in opposite directions through the track rails,

controlling the signaling current in said loop cirifying the phase relation of said current in accordance with the presence or absence of other trains ahead, and then detecting on said train such phase relation.

25. The method of continuous control for train control systems which consists, in providing a loop circuit and a receiving circuit along the trackway one including the track rails in series, inducing from a car-carried source an alternating signaling current in the loop circuit, controlling the electrical connection between the loop circuit and the'receiving circuit in accordance with traflic conditions in advance, and finally detecting the existence of signaling current in the receiving circuit.

26. The method of continuous inductive train control which consists, in communicating between the trackway and a moving train by electro-magnetic induction by utilizing current flowing in the track rails which current is wholly derived from a source of current on the car itself, changing the polarity of the current in accordance with traffic conditions ahead and detecting inductively the modified current on that same car.

27. The method of continuously controlling train movements in accordance with traffic conditions along the trackway in advance of a train which consists, in supplying a signalingrzurrent from ansource of energy wholly on the train to a track'way circuit including the track rails and a controllable translating device, and continuously inductively detecting on the train said current as controlled by the translating device.

28. The method of continuously communicating control influences to moving trains during their progress through blocks having normally closed track: circuits which consists, in inducing in the track rails of-each block an alternating signaling current, controlling that signaling current in accordance with the presence or absence of another train on the track circuit next in advance, and detecting on the following train by magnetic induction through an air gap the signaling current so controlled.

29. The method of continuous control for traincontrol systems which consists, in producing in the track rails in advance of a car an alternating current derived wholly from a source of alternating current on said car, controlling the phasev relation of said signaling current with respect to the producing source in accordance with the presence or absence of other trains ahead, and finally automatically determining on said car the phase relation of said current so controlled.

30. The method of train control which consists, in continuously maintaining train control means on a car which has a tendency to assume its active condition in the inactive condition so long as a predetermined extent of track in advance of the car is unoccupied, by inducing in a loop circuit and a receiving circuit along the track an alternating signaling current derived wholly from a source of energy on the car, one of said trackway circuits including the track rails in series for a predetermined distance in advance of the car so that the flow of signaling current in that circuit isaffected by the shunting action of the wheels and axles of another train, controlling the electrical' connection between said circuits in accordance with the presence or absence of another train still further in advance, and inductively detecting on said car the existence and character of the signaling current in the trackway receiving circuit.

31. The method of train control for railroads having some portions thereof equipped with an alternating current supply and other portions having no trackway source of .alternating current, which consists in supplying to the track rails an alternating signaling current derived from the trackway source where available and from a car-carried source where not available, and inductively detecting such signaling current.

32. The method of train control for railroads in which portions ofthe track have an alternating current in the track rails controllable by the shunting action of wheels and axles of the train and in which other portions of the track have a direct current in the trackrails which consists, in supplying throughout all portions of the railroad an alternating signaling current in the track rails ahead of a car, maintaining or interrupting that signaling current dependent upon the presence or absence of other trains ahead, and detecting by induction the existence and character of said signaling current after being so controlled.

33. The method of train control which consists, in governing an electro-responsive device on a car in accordance with the existence and phase relation of a current on the track rails adjacent to the car which current is produced in the track rails inductively from a source wholly on the car and has its phase relation varied by 105 the presence of'other trains ahead.

34. In a train control system, the combination of biased electro-responsive means on a. car, means inductively responsive to the flow of alternating current in the track rails on which '110 the car is running for governing said electroresponsive means and maintaining it energized under clear trafiic conditions ahead by such current, and means for producing in said track rails an alternating signaling current derived wholly 115 from a source of energy on said car and automatically controlled in accordance with the presence or absence of other trains ahead.

35. In a train control system, a trackway loop circuit and a receiving circuit one including a 120 predetermined length of the track rails in series, car-carried means including a source of alternating current for inducing in the loop circuit a signaling current and for detecting the fiow of such signaling current in said receiving circuit, and means responsive to the presence or absence of trains for controlling the transmitting connection between said loop circuit and said receiving circuit.

36. A continuous control system for railroads 130 having track divided into blocks each equipped with a normally closed track circuit, a wayside circuit for each block including the track rails thereof, means controlling the flow of current in said wayside circuit by the track circuit of the block next in advance, car-carried means for producing in the wayside circuit a signaling current, and car-carried means inductively. controlled by the current in the wayside circuits.

37. In a train control system for railroads having tracks divided into blocks each equipped with a normally closed circuit, a wayside circuit for each block including the track rails thereof in series, another wayside circuit for each block including the track rails in multiple, means controlled by the track circuit of the block next inadvance for governing the transmission connection between said two wayside circuits, means on a car for inducing in one of the wayside cir- 

